[Python] Unexpected behavior trying to add a custom representer to Python yaml module?

I want to dump a dictionary containing ip addresses (as ipaddress.IPv4Network objects) as YAML. Following the docs, I tried the following:

import ipaddress
import yaml


def address_representer(dumper, data):
return dumper.represent_scalar('tag:yaml.org,2002:str', str(data))


yaml.add_representer(ipaddress.IPv4Network, address_representer)
print(yaml.safe_dump({'network': ipaddress.IPv4Network('192.168.1.0/24')}))


But this fails with:

[...]
File "/home/lars/.local/lib/python3.9/site-packages/yaml/representer.py", line 231, in represent_undefined
raise RepresenterError("cannot represent an object", data)
yaml.representer.RepresenterError: ('cannot represent an object', IPv4Network('192.168.1.0/24'))


What am I doing wrong?

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